By means of the film transfer technique, in film size presses the application of a size or paste onto the paper is carried out so that, depending on whether one side or both sides of the paper are supposed to be coated, coating agent films of the desired thickness are spread onto the face or faces of one or both of the rolls in the film size press by means of applicator devices, in which connection these coating agent films are transferred onto the paper web in the nip formed by the size press rolls as the paper web runs through said nip. As a rule, the film rolls in the film size presses are provided with resilient coatings, and the application onto the roll face can be carried out by using some prior-art blade coater, a bar coater provided with a smooth or grooved coating bar, or an equivalent nozzle equipment. At present, in paper machines and, thus, also in the related film size presses, ever higher speeds are aimed at, in which connection in particular this increased speed in size film presses has provided a new problem, i.e., in particular when running takes place with large coating quantities, formation of mist of the coating agent occurs at the outlet side of the press nip. The formation of mist in itself would not be a major problem, but a problem arises when this mist gathers on the constructions of the machine and drips from there onto the paper web and spoils the paper quality, or when the mist spreads into the air in the room. Since the problem has been encountered with higher significance only with increased web speeds, in the prior art at least substantially significant solutions have not been suggested for elimination of this problem.
Indeed, there are some prior-art solutions, and of them can be mentioned, for example, the FI Patent No. 90,266, in whose solution attempts have been made to prevent formation of mist by using a particular hood construction. Similarly, in the FI Patent No. 93,243 a solution is suggested in which the formation of mist in itself is not prevented, but this mist is recovered, or at least attempts are made to recover the mist, by means of mechanical devices fitted at the outlet side of the nip, so that the mist should not have access to other constructions. Thus, this earlier publication does not provide a solution for the formation of mist itself either.